The present invention relates to a method of forming a semiconductor chip, and more specifically to formation of laser chip markers for passive alignment.
The passive alignment has been described in “Synonymous With Alignment-Optical Packaging”, Journal of Japan Institute of Electronics Packaging, Vol. 13, No. 1 (1988), pp 54-56. While a visual type, a mechanical type, and a flip-chip type have been introduced for the passive alignment in the present Journal, the present invention relates to the visual type.
According to the above-described document, the visual type passive alignment is equivalent to one wherein a chip mounter adopted in die bonding of electronic components such as an LSI chip is made high in accuracy. Both a mounting board and an optical chip are provided with eye-alignment markers, and both positions thereof are detected by image recognition. Thereafter, a stage for holding the optical chip is moved to a predetermined position and fixed thereat.
The markers provided on the chip are respectively made up of a metal formed on a silicon oxide film on the surface of the chip. In general, the markers are provided plural per chip and respectively take easy-to-visually recognize shapes such as round shapes.
Since, however, the markers on the chip are formed on the silicon oxide film, they might produce imperfections that the metal surfaces of the markers are flawed, the shapes thereof are reduced or become large in reverse, or the markers are deformed and peeled as the case may be. When the imperfections occur in such markers, a problem arises in that the chip cannot be packaged on a mounting board due to passive alignment even if the chip per se is a non-defective item free of any problem in terms of its characteristic.